Control of Droplet Impact through Magnetic Actuation of Surface Microstructures

Abstract

An effective method for on‐demand control over the impact dynamics of droplets on a magnetoresponsive surface is reported. The surface is comprised of micrometer‐sized lamellas from a magnetoactive elastomer on a copper substrate. The surface itself is fabricated using laser micromachining. The orientation of the lamellae is switched from edge‐on (orthogonal to the surface) to face‐on (parallel to the surface) by changing the direction of a moderate (<250 mT) magnetic field. This simple actuation technique can significantly change the critical velocities of droplet rebound, deposition, and splashing. Rebound and deposition regimes can be switched up to Weber number We < 13 ± 3, while deposition and splashing can be switched in the range of 32 < We < 52. Because a permanent magnet is used, no permanent power supply is required for maintaining the particular regime of droplet impact. The presented technology is highly flexible and enables selective fabrication and actuation of microstructures on complex devices. It has great potential for applications in soft robotics, microfluidics, and advanced thermal management.

Tunable rebound of millimeter-sized rigid balls by magnetic actuation of elastomer-based surface microstructures

“…The measurement setup from [29] was modified to implement the falling of small solid balls. Figure 1 shows a schematic diagram of the setup.…”

“…In this case, the field-induced changes in the MAE properties seem to have no direct effect on the ball rebound. In the present paper, we also utilize magnetic fields to affect the rebound characteristics of balls from 'smart' elastomeric surfaces but achieve it by changing its surface topography, similarly to the idea used in [29] for controlling the outcome of the impact of water droplets.…”

Surface Modification of Magnetoactive Elastomers by Laser Micromachining

“…Such lamellae can be employed for the transportation of liquid droplets and solid objects [53,54]. Lamellar surfaces also provide control of the droplet impact [55] and switchable wettability [47,52].…”